Many parts of the Earth are truly astonishing to behold. One of them lies beneath the Chihuahuan Desert, which stretches from northern Mexico down south and into western Texas. Hidden underground is a cave filled with giant crystals—towering pillars and bulbous formations with rough surfaces.
Even on the desert’s surface, there is plenty to capture attention: clumps of spiky Ocotillo plants, eye-stinging dust storms, and the fragrant aroma from chili plantations.
When night falls, the temperature cools, and desert wildlife emerges. Coyotes, pronghorns, and mule deer roam in search of food. Kangaroo rats sneak beneath creosote bushes, hoping to sip moisture from the leaves while avoiding deadly rattlesnakes.
Yet the wonder does not stop at the surface. Deep below lies another treasure waiting to be explored—a forest of massive crystals formed over hundreds of thousands of years.
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Discovery of the World’s Largest Crystal Formation
The crystals were first discovered about a quarter of a century ago, when two brothers drilled a ventilation shaft for their mining project in Chihuahua, Mexico. At a depth of 300 meters, they stumbled into a cave the size of a basketball court. What they saw left them speechless: an entire chamber filled with gigantic crystals—the largest ever found on Earth. The site soon became known as the “Cave of Crystals.”
When the brothers shone their lights inside, they saw a tangled labyrinth of massive selenite crystals, some almost beyond description. The largest stretched 11 meters in length and weighed an estimated five tons.
The crystals, milky white and translucent, filled the chamber in otherworldly patterns, creating a sight so extraordinary it left observers momentarily speechless.
“There is no other place on the planet where the mineral world reveals itself in such beauty,” said Juan Manuel García-Ruiz, a geologist from the University of Granada, to National Geographic in 2007.
García-Ruiz and his team sought to understand how this natural wonder formed. To do so, they studied tiny pockets of water trapped within the crystals. Their research pointed to the influence of magma, much like in other remarkable geological sites around the world.
Beneath the cave, about 4 kilometers deep, lies a massive pool of magma releasing constant heat. At some point in the past, the cave filled with mineral-rich water containing anhydrite. Over a million years, magma kept the water at a steady 58°C, dissolving the anhydrite into gypsum. That gypsum eventually crystallized into the giant selenite formations we see today.
A Small Hell Underground
The Cave of Crystals consists of at least four known chambers: the Crystal Cave, Queen’s Eye Cave, Candle Cave, and Ice Palace. The phrase “at least” is used because, even 25 years after its discovery, the cave system has not been fully explored.
Inside, temperatures can soar to 58°C, close to record highs in Death Valley. But more dangerous than the heat is the humidity, which can reach 90 to 100 percent. Such conditions can kill a human in minutes.
For this reason, when scientific exploration first began, special engineering was required. A team led by cave mineral specialist Paolo Forti of the University of Bologna developed custom cooling suits.
The suits were based on standard caving gear but outfitted with thick tubing connected to a backpack holding 20 kilograms of ice and water. The cooling fluid circulated through the tubes while a refrigerated breathing system kept explorers alive.
“With that technology, even as advanced as it was, you could only stay cool for about thirty minutes,” explained Forti.
The crystals themselves posed another challenge. Photographs show just how physically demanding it was to navigate the cave. Exploration revealed potential additional chambers, but reaching them would require breaking through some crystals—a step no caver was willing to take.
Exploration Halted
Scientific operations were suspended in 2015, following the closure of mining in the area. Still, in just 15 years, researchers made significant discoveries. Paleobotanists, geochemists, geologists, and hydrogeologists had the chance to study the extraordinary formations.
Interestingly, biologists joined the effort too. They hoped the crystals had trapped traces of ancient DNA when they formed in hot mineral-rich water millions of years ago. For a while, nothing was found. But in 2017, speleologist and extremophile expert Penelope Boston from the New Mexico Institute of Mining and Technology announced an incredible discovery of ancient bacteria preserved within crystal samples collected before the cave was re-flooded. The bacteria were unique, unlike any known species on Earth.
For now, the cave remains closed to human exploration, though that could change if mining operations resume. For scientists, the closure means the postponement of further discoveries locked within the crystals. But perhaps there is some comfort in knowing that the Cave of Crystals has returned to the same untouched state it was in when it was first discovered. (Sulung Prasetyo)
